Our study of a transgenic mouse line which overexpresses heat shock protein (hsp) 70 is progressing in two directions. Using 23Na NMR with TmDOTP5- as the shift reagent, we characterized the effect of global ischemia on intracellular sodium (Nai) accumulation and determined the NMR visibility of Nai in the mouse heart by comparing NMR versus atomic absorption-derived measurements of Nai in the wild type mouse heart. So that we can test the hypothesis that overexpression of hsp70 in the liver is associated with reduced cell injury following ischemia, we have also established the feasibility of both 23Na NMR using TmDOTP5- and 31P NMR of the perfused mouse liver for the measurement of Nai and PCr, ATP, Pi and pH respectively. We have also developed a collaboration with Dr. Lefkowitz at Duke University to assess the effect of transgenic alterations in beta-adrenergic stimulation on post-ischemic recovery of the Langendorff perfused heart using 31P NMR spectroscopy. We have completed preliminary experiments with 3 different lines (and their wild type siblings) which overexpress beta 2-adrenergic receptors, beta-adrenergic receptor kinase-1, or beta-adrenergic receptor kinase-1 inhibitor. Surprisingly, in this model, those hearts with augmented contractility do not appear to have impaired recovery following global ischemia. Finally, we have completed a series of experiments in the rat heart to interrogate changes in NMR visibility of intracellular potassium (Ki) (using TmDOTP5- as a shift reagent) during ischemia. Using rubidium as a substitute for potassium, in both NMR and atomic absorption experiments, there appears to be an NMR invisible pool of Ki which becomes visible during ischemia thus rendering NMR spectroscopy unsuitable as a method for measurements of total Ki during ischemia in the perfused heart.